1. Parity Violation in the  decay of polarized 93 Tc 17/2 - isomers B.S. Nara Singh, M. Hass and G. Goldring Weizmann Institute of Science, ISRAEL D. Ackerman, J. Gerl, F.P. Hessberger, S. Hofmann, I. Kojouharov,P. Kuusiniemi, H. Schaffner, B. Sulignano GSI, Germany B. A. Brown NSCL, Michigan, USA Motivation Experiment Results Future

2. B.S. Nara Singh et. al. 1956: Lee & Yang, Parity Non-Conservation (PNC) discovery. H pnc different behavior under Parity operation. 1957: Wu et al. Measure PNC in  -decay of polarized 60 Co. 1958: Feynman & Gell-mann suggest first-order weak interaction in the nuclear potential (PV nuclear force). Consequence PNC in N-N systems. Adelberger & Haxton, Ann. Rev. Nucl. Parti. Sci. 35(1985). Only accessible to study neutral current WI between quarks. H weak =H L +H SL +H NL (  S=1)+H NL (  S=0) PV in Nuclei : Probes H NL (  S=0); together with N-N scattering data it establishes IS, IV and IT strengths. An avenue full of surprises. Not just a check on SM Motivation

3. B.S. Nara Singh et. al. Observable Parity mixing in the nuclear energy levels shows up in EM and Strong decay. EM transitions: Circular Polarization in  radiation from Unpolarized nuclei Up-down asymmetry of  radiation following polarized thermal neutron capture  decay angular distribution from polarized nuclei

4. B.S. Nara Singh et. al. Only Few Cases 18 F < 90 meV 19 F ~ 380(100) meV 21 Ne < 30 meV 93 Tc ~0.59(19)(25) meV 180 Hf~1.0(0.1)  eV In the presence of 10 7 times strong interaction. Yet significant due to Structural effects.

5. B.S. Nara Singh et. al. Parity doublet at 300 eV Proximity. N=50, Reasonable nuclear Structure Calculations within Shell model. Establishes IT component and complementary to the studies in light nuclei. Unique case For non-zero PNC.

6. B.S. Nara Singh et. al. 45 Sc( 52 Cr, 2p2n) 93 Tc E lab ( 93 Tc) = 65 MeV Checked with Si-det. Separates and Transfers to Focal Plane Area M. Hass et al., PLB 371, 25, previous work at SHIP- GSI, RMS-LNL TF technique for Polarization Stepper Motor 2 mins. + 1sec 16 foils, @70º 15-15  g/cm2 0-180° Asymmetry (A  ) in the M2/E3(  )  -decay due to E2 Component

7. B.S. Nara Singh et. al. 45 Sc 1mg/cm 2 16 foils, @70º 15-15  g/cm2 Setup High count rate handling Counts in 751 keV line, 6M per crystal

8. B.S. Nara Singh et. al. Triple Ratios & A  Independent of Gamma efficiency Beam current fluctuation and experimental artifacts

9. B.S. Nara Singh et. al. Results p l = 0.15 known from QP interaction measurements M. Hass et al., PRC 43, 2140. AveragePresentPLBE(keV) 1.00056(63)0.99912(122)1.00107(73)544(93Ru) 1.00068(41)1.00088(66)1.00055(53)629(93Tc) 0.99977(28)0.99962(41)0.99989(38)711(93Tc) 0.99904(43)1.00028(71)0.99833(54)751(93Tc) 0.99947(67)0.99972(112)0.99933(84)1392(93Ru) 1.00015(24)1.00038(31)0.99977(39)1432(93Tc)

10. B.S. Nara Singh et. al. Results Present+PLB, 371, 25: A  = 4.8 (2.1). 10 -4, =0.34(14)(25) meV Theory: 1p 1/2 -0g 9/2 with IV strength correction by an empirical factor of 0.15±0.15. = - 0.2 to 1 meV Preliminary

11. B.S. Nara Singh et. al. Future More experiments on 93 Tc (??) 180 Hf: Huge structural effect. Low magnitude for. Need for an independent check. Technique : Low T orientation with NICOLE ISOLDE, CERN and  asymmetry. Successful Test run, Oct.04, Production run, May, 05